A recent study published in Engineering offers a comprehensive review of the detection of hydrate blockages in subsea oil and gas pipelines, which is crucial for ensuring the smooth operation of the oil and gas industry.

As offshore oil and gas exploration moves deeper into the ocean, the issue of hydrate blockages becomes more severe. Hydrates can form, accumulate, and settle in pipelines, which increases flow resistance, reduces transport capacity, and may even lead to pipeline ruptures, which may cause significant economic losses and potential safety hazards.

The researchers from institutions like Dalian University of Technology summarized the characteristics of hydrate formation and blockage from multiple aspects. Thermodynamically, hydrate formation is an exothermic process that consumes gas, leading to pressure drops and temperature changes in the system. Acoustically, the presence of hydrates affects the propagation of acoustic waves, and the impedance mismatch between hydrates and the surrounding medium can be used for detection. Electrically, hydrates have distinct electrical properties, such as low conductivity, and their formation can cause changes in resistivity and dielectric constant. In terms of flow characteristics, hydrates can alter the flow patterns, increase pressure drops, and change the slurry viscosity.

The paper also analyzed various detection methods. Acoustic pulse reflectometry is effective for long-distance blockage detection in both onshore and subsea environments, while transient-based methods offer rapid response and high accuracy, but their application in gas pipelines remains under-researched. These methods can detect blockages by analyzing the reflection of acoustic or transient waves. For example, acoustic pulse reflectometry can determine the location and length of blockages based on the impedance difference. However, they also face challenges, such as the need for accurate acoustic velocity estimation and signal denoising. Other methods like the eigenfrequency shift, vibration analysis, ultrasonic guided wave, and electrical methods have their own advantages and limitations. For instance, the eigenfrequency shift method can detect blockages by changes in the characteristic frequency of the pipeline, but it requires historical data for accurate results.

In addition, the article introduced the engineering applications of these detection methods. Some teams have conducted onsite experiments, and many commercial products are available in the market. For example, acoustic pulse reflectometry has been used to detect defects in pipelines of different lengths and diameters under various conditions.

Looking ahead, the researchers proposed future directions. They suggest developing algorithms to balance the detection distance and accuracy of acoustic waves, improving the performance of sensors in complex subsea environments, and integrating multiple detection methods to enhance the reliability of blockage detection. This research provides valuable insights for the development of more effective hydrate blockage detection techniques, which will contribute to the safe and efficient operation of subsea oil and gas pipelines.

The paper “Hydrate Blockage in Subsea Oil/Gas Pipelines: Characterization, Detection, and Engineering Solutions,” authored by Yang Meng, Bingyue Han, Jiguang Wang, Jiawei Chu, Haiyuan Yao, Jiafei Zhao, Lunxiang Zhang, Qingping Li, Yongchen Song. Full text of the open access paper: https://doi.org/10.1016/j.eng.2024.10.020. For more information about the Engineering, follow us on X (https://twitter.com/EngineeringJrnl) & like us on Facebook (https://www.facebook.com/EngineeringJrnl).